The present invention relates to fiber optic cross connects, and more particularly to the population of a substrate in fiber optic cross connects.
The use of optical cross connect (OXC) switching systems are well known in the art for directing a light beam from one optical port in an optical transmission system to another optical port. In a typical OXC, a plurality of input optical fibers, or ports, carry light beams into the OXC. The OXC then directs, or switches, the light beams to their respective plurality of output ports. Many conventional OXCs perform the switching utilizing micromirrors, which are micro-machined onto a substrate. The micromirrors are used to reflect a light beam from an input port to a particular output port. In this specification, the words xe2x80x9cinputxe2x80x9d and xe2x80x9coutputxe2x80x9d are used to indicate a direction of travel for a light beam into and out of, respectively, a switch. In reality, the input and output ports can be used simultaneously for input and output, as is the case in bidirectional data transfer.
High port count switches utilizing micromirrors are of high demand in the industry. Such switches require a tight packing density of the micromirrors onto the substrate. Some conventional switches use a digital switching matrix for N input and N output ports with an Nxc3x97N array of micromirrors. This requires a total of N2 number of micromirrors. However, this architecture becomes impractical for switch port counts greater than a few hundred.
Some conventional switches use an analog switching matrix for N input and N output ports. This requires 2*N micromirrors. In this configuration, two separate substrates, or one very large substrate, are necessary to accommodate port counts greater than a few hundred. However, the use of more than one substrate is cumbersome as they need to be aligned to each other within the package of the switch. This adds complexity to the assembly of the package and increases package size. Also, with a hundred or more micromirrors on a single substrate, or one half of a two-substrate OXC, device yield is compromised due to the large number of possible failure points. Additionally, hermetically sealing the optical components requires additional complex steps in the manufacturing process, such as metallization of the fibers or optical component attached to the fibers.
Accordingly, there exists a need for an improved OXC package which provides a high port count while also providing a high device yield. The present invention addresses such a need.
The present invention provides a fiber optic cross connect (OXC) package which utilizes a modular approach to substrate population. The OXC includes a slab, where the slab comprises a first surface and a second surface, and a micromirror array coupled to the second surface of the slab, where the micromirror array comprises a plurality of clusters, where each of the plurality of clusters includes at least one micromirror of the micromirror array. In the preferred embodiment, the slab is a substrate. Chips containing micromirrors are fabricated in clusters so that groups of micromirrors can be separately placed onto the substrate. This provides flexibility in how the substrate is populated. In the preferred embodiment, the clusters are in the form of strips. Only strips with known good micromirrors are placed onto the substrate, thus improving the device yield. Also, if any of the micromirrors become damaged after placement, its chip may be replaced without disturbing the other chips. Using a substrate through which light may travel in combination with a modular approach to substrate population allows for a single substrate switch with a higher device yield and scalability. Integrated circuits may be placed on the same substrate as the micromirrors, and the complexity of the assembly process is reduced.